Mapping the Structure and Metasomatic Enrichment of the Lithospheric Mantle Beneath the Kimberley Craton, Western Australia

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Abstract

<div>The lithology, geochemistry, and architecture of the continental lithospheric mantle (CLM) underlying the Kimberley Craton of north-western Australia has been constrained using pressure-temperature estimates and mineral compositions for >5,000 newly analyzed and published garnet and chrome (Cr) diopside mantle xenocrysts from 25 kimberlites and lamproites of Mesoproterozoic to Miocene age. Single-grain Cr diopside paleogeotherms define lithospheric thicknesses of 200–250 km and fall along conductive geotherms corresponding to a surface heat flow of 37–40 mW/m 2. Similar geotherms derived from Miocene and Mesoproterozoic intrusions indicate that the lithospheric architecture and thermal state of the CLM has remained stable since at least 1,000 Ma. The chemistry of xenocrysts defines a layered lithosphere with lithological and geochemical domains in the shallow (<100 km) and deep (>150 km) CLM, separated by a diopside-depleted and seismically slow mid-lithosphere discontinuity (100–150 km). The shallow CLM is comprised of Cr diopsides derived from depleted garnet-poor and spinel-bearing lherzolite that has been weakly metasomatized. This layer may represent an early (Meso to Neoarchean?) nucleus of the craton. The deep CLM is comprised of high Cr2O3 garnet lherzolite with lesser harzburgite, and eclogite. The peridotite components are inferred to have formed as residues of polybaric partial mantle melting in the Archean, whereas eclogite likely represents former oceanic crust accreted during Paleoproterozoic subduction. This deep CLM was metasomatized by H2O-rich melts derived from subducted sediments and high-temperature FeO-TiO2 melts from the asthenosphere.</div><div><br></div><div>Geoscience Australia’s Exploring for the Future program provides precompetitive information to inform decision-making by government, community and industry on the sustainable development of Australia's mineral, energy and groundwater resources. By gathering, analysing and interpreting new and existing precompetitive geoscience data and knowledge, we are building a national picture of Australia’s geology and resource potential. This leads to a strong economy, resilient society and sustainable environment for the benefit of all Australians. This includes supporting Australia’s transition to net zero emissions, strong, sustainable resources and agriculture sectors, and economic opportunities and social benefits for Australia’s regional and remote communities. The Exploring for the Future program, which commenced in 2016, is an eight year, $225m investment by the Australian Government.</div><div><br></div><div><strong>Citation:</strong></div><div>Sudholz, Z.J., et al. (2023) Mapping the Structure and Metasomatic Enrichment of the Lithospheric Mantle Beneath the Kimberley Craton, Western Australia, <em><i>Geochemistry, Geophysics, Geosystems</i>,</em> 24, e2023GC011040.</div><div>https://doi.org/10.1029/2023GC011040</div>

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document

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147708

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Commonwealth of Australia (Geoscience Australia)
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Keywords

( Project )

EFTF – Exploring for the Future

( Project )

Lithospheric Geophysics

( Project )

Australia's Resources Framework

Argyle

Ellendale

Kimberley Craton

North Australia Craton

SCLM

Sub-Continental Lithospheric Mantle

Cratonic Lithosphere

Geothermobarometry

Diamond Exploration

Xenoliths

Xenocrysts

theme.ANZRC Fields of Research.rdf

Earth SciencesInorganic geochemistryIgneous and metamorphic petrologyGeothermics and radiometricsEarth system sciences

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Publication Date

2023-10-19T01:02:37

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2023-04-04T06:00:00

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completed

Purpose

Journal article detailing the lithospheric structure and composition of the Kimberley Craton, Western Australia. Mantle xenoliths from the continental lithospheric mantle were collated and analysed to provide constraints on the geochemical composition and geothermal profile of the lithosphere at the time of their exhumation.

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geoscientificInformation

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Geochemistry, Geophysics, Geosystems Vol 24 Issue 9

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<div>A dataset of approximately 4000 garnet and Cr diopside analyses has been compiled. With the exception of Argyle xenolith data analyses taken from Jaques et al., (1990, 2018) and Luguet et al., (2018), all Cr diopside and garnet were sourced from heavy mineral concentrate and/or diamond inclusions from kimberlite and lamproite pipes. Our dataset also includes previously unpublished analyses from several intrusions across the Kimberley Craton.</div><div><br></div><div>Quantitative analyses of major and minor oxides were performed using electron probe microanalyzer (EPMA) at the Centre for Advanced Microscopy, the Australian National University. The concentrations of trace element isotopes in garnet and Cr diopside were measured by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) at the Research School of Earth Sciences, Australian National University.</div><div><br></div><div>Equilibration pressure-temperature (PT) of Cr diopside xenocrysts were determined using the single-grain Cr-in-clinopyroxene geobarometer of Sudholz et al. (2021a) and enstatite-in-clinopyroxene single-grain geothermometer of Nimis and Taylor (2000). The filtering of Cr diopside PT estimates followed the protocols of Ziberna et al., (2016). All PT estimates were calculated using the PTEXL spreadsheet (maintained by T. Stachel, University of Alberta). Estimates of equilibration T for pyrope garnet were made using the experimentally calibrated single-grain Ni-in-garnet geothermometer of Sudholz et al. (2021b), using garnet Ni concentrations measured by LA-ICP-MS and an olivine Ni concentration of 3000 ppm. The filtering of Ni-in-garnet T estimates followed the protocols of Sudholz et al., (2021b). The equilibration P of garnet were determined by referencing Ni-in-garnet T estimates to the local geotherm defined by the Cr diopside xenocrysts. The source lithology of the analysed pyrope garnet was identified using the modified version of the G-number classification scheme for mantle garnets (see Sudholz et al. 2022b) (modified after Grütter et al., 2004). The Mg# of olivine (Mg#olv = Mg/ (Mg + Fe)) coexisting with garnet in peridotite was determined by inverting the garnet-olivine Fe-Mg exchange geothermometer of O’Neill and Wood (1979) to solve for Ni-in-garnet T (see Sudholz et al. 2022b). Paleogeotherms for each intrusion were modelled in FITPLOT (Mather et al., 2011) using the PT estimates from Cr diopside.</div>

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[-19, -13, 129, 123]

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